Plural beam electron discharge devices



June 28, 1955 w. L. FITE ETAL PLURAL BEAM ELECTRON DISCHARGE DEVICES Filed Sept. 4. 1952 MAJ ATTORNEY PLURAL BEAM ELECTRON DISCHARGE DEVICES Wade L. Fite, Jenkintown, and Albert D. Rittmann, Philadelphia, Pa, assignors to Philco Corporation, Phiiadeiphia, la., a corporation of Pennsylvania Application September 4, 1952, Serial No. 307,868

13 Claims. (Cl. 313-69) The present invention relates to electron discharge devices and more particularly to improved electron discharge tube assemblies adapted to generate a plurality of individually controllable electron beams. The invention is particularly applicable to cathode-ray tubes embodying an electron gun assembly adapted to produce a plurality of electron beams, the intensities of which are individually controllable, and the invention will be specifically described in this connection. It should be Well understood, however, that the invention is also applicable to other forms of electron discharge devices embodying a common assembly for generating two or more electron beams, the intensities of which may be individually controlled to impart individual characteristics to the respective beams.

Cathode-ray tubes embodying a plurality of electron beams, the intensities of which may be individually controlled, are commonly used for reproducing color television images. In one form of such tube, each of the beams may be individually varied in accordance with a different one of a plurality of signals, each representing variations of a ditferent primary color content of the image to be reproduced, and may be made to impinge selectively on a corresponding one of a plurality of phosphor materials constituting a common image screen structure and adapted to produce light of the different primary colors.

In another form, such tubes may be used in the color television system disclosed and claimed in the copending application of Melvin E. Partin, Serial No. 242,264 filed August 17, 1951. As disclosed in that application, a dual beam cathode-ray tube is utilized in a manner such that one of the beams is varied in intensity by an applied color video Wave and is adapted to energize an image reproducing screen structure comprising successively arranged groups of phosphor stripes, each stripe of each of the groups being adapted to produce light of a different primary color. The second beam is simultaneously scanned over the screen structure with the first beam by means of a common deflection system. By independently varying the intensity of the second beam by means of a pilot carrier signal having a frequency outside of the frequency spectrum of the color video Wave, and by employing a series of indexing portions also contained on the screen structure, an indexing signal is produced which is indicative of the position of the beams. This indexing signal is used to establish the time phase position of the color video wave relative to the scanning position of the beams, thereby insuring that the intensity variations of the first beam occur in consonance with the impingement of the different light producing phosphor stripes by the beam.

In order to serve these functions adequately, it is essential that the intensity of each beam be individually controllable without significantly affecting the intensity of the other beam or applying a deflecting force thereto. Furthermore, since, in the pilot carrier indexing system above outlined, the position of one of the beams is in- 2,712,037 Patented June 28, 1955 dicative of the position of the other beam, it is desirable that both beams maintain a fixed position relative to each other throughout the scanning area of the image screen. This requires that both beams be treated as a single beam by the focusing and deflection elements of the cathoderay tube. To fulfill these requirements, the two beams should be generated relatively close to each other and, in a typical case, the spacing between the axes of the generated beams may be of the order of .040 inch. Furthermore, in order to insure that the beams shall be uniformly responsive to the focusing and deflection influences of the tube system, the emission surfaces and the intensity control surfaces of the beams should be identically spaced relative to the common accelerating, focusing and deflection regions.

In view of these requirements, the beam generating and intensity control systems of the beams must be made and assembled with great precision. Furthermore, it is necessary that the precision established in the manufacture of the beam system be maintained in the subsequent operation of the tube notwithstanding mechanical shocks to which the tube may be subjected prior to its installing in the receiver in which it is to be used, and notwithstanding the changes in the temperature of the various tube components normally occurring in the operation of the cathode-ray tube.

It is an object of the invention to provide an improved electron discharge tube assembly adapted to generate a plurality of individually controllable electron beams.

A further object of the invention is to provide an improved assembly for the beam generating and control system of a multiple beam electron discharge tube, which assembly can be made to close geometric tolerances in a facile and economic manner.

A specific object of the invention is to provide an improved generating and intensity control assembly for a multiple beam cathode-ray tube, which assembly can be made with great precision and is adapted to produce multiple beams which are closely spaced relative to each other and which exhibit substantially identical characteristics.

Another object of the invention is to provide an improved generating and control assembly for a multiple beam cathode-ray tube, which assembly is robust and retains its initially established operating characteristics notwithstanding mechanical shocks and thermal changes to which the assembly may be subjected.

Further objects of the invention will appear as the specification progresses.

In accordance with the invention on the foregoing objects are achieved by a novel multiple beam gun assembly wherein an electron emissive body, serving to provide a common cathode surface for the beams, is contained within an assembly serving as a common support for a plurality of substantially coplanarly supported intensity control electrodes. It is a feature of the invention that the intensity control electrodes are in the form of individual spade elements symmetrically positioned relative to each other and to the common emission surface by means of a common mechanical supporting system also serving to individually electrically insulate the control electrodes.

The invention will be described in greater detail with reference to the appended drawings forming part of the specification and in which:

Figure l is a plan view, partially in cross-section, showing a cathode-ray tube embodying the novel multiple beam generating and intensity control assembly of the invention;

Figure 2 is a cross-sectional view of one form of a dual beam generating and intensity control assembly in accordance with the invention;

Figure 3 is a plan view of the assembly in Figure 2;

Figure 4 is a perspective view of one embodiment of the intensity control electrodes of the assembly of the invention; and

Figure 5 is a perspective view of another embodiment of the intensity control electrodes of the assembly of the invention.

Referring to Figure l, the cathode-ray tube shown therein comprises an evacuated envelope of well known form consisting, for example, of glass. velope 10 there are arranged a dual beam generating and controlling system 12 in accordance with the invention and later to be more fully described, a focusing electrode 14, and a beam accelerating electrode 16 which may consist of a conductive coating on the inner wall of the envelope in conformity with well established practice.

The end face 18 of the envelope may be provided with a beam intercepting structure, the actual construction of which is determined by the particular function which the cathode-ray tube is to serve. In one instance, for example, the cathode-ray tube may be used for producing a color television image in a system of the type disclosed in the above mentioned Partin application, in which case tie beam intercepting structure arranged at the face plate may comprise consecutively arranged groups of phosphor stripes, the stripes of each of the groups being adapted to produce light of three different primary colors upon impingement by one of the beams generated by the dual beam generating and control system 12. In such an arrangement, the beam intercepting structure may further comprise index signal generating portions having a geometric configuration indicative of the geometric configuration of the phosphor stripes and adapted to produce an appropriate indexing signal upon impingement by the second of the beams emanating from the dual beam generating and control system 12. A beam intercepting screen structure of the foregoing type has been described in detail in the above-mentioned Partin application and a further description thereof in the present application is be lieved to be unnecessary.

One embodiment of a dual beam generating and control assembly in accordance with the invention is shown in Figures 2 and 3. As shown therein, the assembly comprises a cylindrical member 20 having a tubular body portion 22 extending into an annular end portion 24. The portion 24 may be formed as a separate element and thereafter suitably secured-by welding, brazing or the like--to the body portion 22, but is preferably formed as an integral portion of the body portion 22, for example by extrusion. Portions 22 and 24 may consist of nickel,

stainless steel or of other suitable material commonly used in the manufacture of gun assemblies for cathode-ray tubes. At the junction of the body and end portions 22 and 24, the tubular portion 22 is provided with peripheral slots 26 and 28.

Within the sleeve 20 are two control electrodes 34 and 36, each in the form of a spade element extending through the peripheral slots 26 and 28 and towards the central axis of the sleeve 20. At their inner portions adjacent to the axis of sleeve 20 electrodes 34 and 36 are each provided with an aperture shown as 38 and 4-8 respectively, through which pass the respective beams to be individually controlled. The apertures 38 and may be made with equal dimensions in the event that identical beams are desired, or may be made with different dimensions in the event that non-similar beams are desired.

Electrodes 34 and 36 are rigidly supported in an electrically insulated manner within the sleeve 20 by means of electrically insulating washers 44 and 46 and by means of a flanged metal ring 48 which may be Welded to the inner surface of the sleeve 20. As will be noted, washer 44 is interposed between the electrodes 34.% and the inner surface of the annular end portion 24, whereas washer 46 is arranged between the said electrodes and the ring 48. By adjusting the compression exerted by the Within the enring 48 against the washer 46, the control electrodes 34 and 36 may be securely positioned within the sleeve 25 The adjustment by the ring 48 is preferably efi'ected after precisely aligning the electrodes so that the apertures 38 and 40 thereof are arranged on a common diameter and the abutting surfaces of the electrodes form a uniform gap 42 having a width of the order of .602", which has been found to be sufficiently small to establish an eiectrostatic field such as to prevent electrons from passing through the gap under normal operating conditions of the cathode-ray tube.

Preferably, and as shown, the width of the exposed portions of electrodes 34 and 36 is smaller than the inner diameters of the washers 44 and 46 so that the likelihood of short conduction paths between the electrodes, brought about by condensation of the emitting material on the washers, is obviated.

in practice, the insulating washers 44 and 46 consist of mica, however, it will be apparent that other suitable stable insulating materials, such as ceramic materials, may be used.

Also positioned within the sleeve 24) is a cathode assembly 3% which may consist of a nickel or stainless steel sleeve 31 open at the bottom end thereof and closed at the top end by a nickel cap 33 to provide a suitable base for an electron emissive coating 32. Coating 32 may be of conventional composition and may consist, for example, of a mixture of barium and strontium oxides.

The cathode assembly 30 is secured Within the sleeve 2% by means of an apertured ceramic disc 50 of steatite, lavite or the like to which the assembly 3t) is affixed by headings 52 and 54 formed on the periphery of the sleeve 31. For locating the disc 59 within the sleeve 20 there are provided an annular spacer 56, consisting of an insulating material-for example a ceramic such as steatite, lavite or the like-one end of which abuts the exposed surface of the mica washer 46 and the other end of which abuts the top surface of the disc 50, and a metal flanged ring 58 which abuts the lower surface of the disc 59 and is Welded or otherwise secured to the inner surface of the sleeve 20.

In order to position the electrodes 34 and 36 in a common plane and at a fixed, predetermined distance from the surface of the electron emitting coating 32, insulating spacers 44 and 46 are formed with substantially flat parallel surfaces, and the spacing determining elements are formed to precisely controlled dimensions. This may be most simply effected by the use of mica for the spacers 44 and 46 as above pointed out, since this material splits with substantially parallel surfaces and can be accurately controlled as to its thickness, and by grinding the active surfaces of the spacer 56 and the disc 50.

A suitable electrical heater (not shown) of well known form may be enclosed within the cathode sleeve 31 to maintain the emissive coating 32 at its electron emitting temperature.

Electrical connection to the cathode sleeve 31 may be provided by a tab 6! welded thereto, whereas individual electrical connections to the electrodes 34 and 36 may be provided by tab extension portions 62 and 64 respectively of these electrodes. In practice, the sleeve 20 may be operated at cathode potential and for this purpose it may be provided with a tab connection 66.

The assembly may be supported within the tube envelope by means of supporting cars 68 which are fused to glass rods '70 (see Figure l) which similarly support the focusing anode 14, and by means of wire standards serving as the connecting elements for the electrodes.

The assembly may be centered within the neck of the cathode-ray tube envelope 10 by a ribbed disc 72 which is welded to the anode 14 and the ribs of which bear against the inner wall of the neck of the envelope.

In some instances it may be desirable to converge the beams emanating from the multiple beam assembly so that both beams are coincident upon impingement on the beam intercepting screen. This may be effected, in accordance with a further feature of the invention, by modifying the shape of the intensity control electrodes as shown in Figures 4 and 5. In Figure 4, two spade shaped electrodes shown at 80 and 82 are formed with a semi-spherical shape at the portions thereof positioned over the surface of the emission coating. In the arrangement shown in Figure 5 two electrodes shown as 84 and 86, are bent with their end portions at an acute angle 0 to the common plane of the remainder of the electrodes so that their active surfaces are arranged at an angle to the surface of the cathode coating. By so modifying the shape of the electrodes, an electron optical analogue of a biprism of index of refraction less than unity is achieved, whereby the plane of the virtual object of the multiple beam system is made to coincide with the plane of the crossovers of the individual beams. The electron lens system will then operate as if the beams originated from a single crossover.

While we have described our invention by means of specific examples and in a specific embodiment, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What We claim is:

1. An electron discharge device adapted to produce a plurality of electron beams individually controllable in intensity, comprising a tubular member having a body portion and a support member provided with a central aperture secured to one end of said body portion, said body portion being provided with a peripheral aperture, a cathode body having an electron emissive surface arranged within said tubular member, electron accelerating means arranged in spaced cooperative relationship to said emissive surface, first and second beam intensity control electrodes each having an active beam forming portion and a planar body portion, said active portions being arranged in spaced abutting relationship between said emissive surface and said accelerating means and the body portions of said electrodes being arranged substantially in parallel planes with the body portion of said first electrode extending through said peripheral aperture, a first electrically insulating member interposed between said support member and one side of the body portion of said first electrode, a second electrically insulating member, means to secure said second insulating member in abutting relationship to the other side of the body portion of said first electrode, and means to position said cathode body with the electron emissive surface thereof adjacent to the inner surface of the active portions of said control electrodes.

2. An electron discharge device as claimed in claim 1 wherein said first and second electrodes are each provided with an aperture in the region of the abutting p0.- tions thereof.

3. An electron discharge device as claimed in claim 1 wherein said body portion of said tubular member is provided with a second peripheral aperture, wherein the body portion of said second intensity control electrode extends through said last mentioned aperture, and further comprising an insulating member interposed between said support member and one side of the body portion of said second electrode, another electrically insulating member arranged against the other side of the body portion of said second electrode, and means to secure said last named insulating member in abutting relationship to the last mentioned side of the body portion of said second electrode.

4. An electron discharge device as claimed in claim 1 wherein said support member comprises an annular disc member integral with the body portion of said tubular member and connected thereto at the outer periphery of the said disc member.

5. An electron discharge device as claimed in claim 1 wherein said means for positioning said cathode body comprises an annular disc member surrounding said cathode body and having its outer edge abutting the inner surface of the body portion of said tubular member, and further comprising an annular sleeve member interposed between said last mentioned disc member and the body portions of said electrodes, said annular sleeve member having an outer dimension greater than an inner dimension of the central aperture of said support member.

6. An electron discharge device as clairned in claim 1 wherein the active portions of said control electrodes are coplanar with the body portions of said electrodes.

7. An electron discharge device as claimed in claim 1 wherein the active portions of the said control electrodes have a hemispherical contour.

8. An electron discharge device as claimed in claim 1 wherein the active portions of the said control electrodes form an acute angle to the plane of the body portions of said electrodes.

9. An electron discharge device adapted to produce two electron beams individually controllable in intensity, comprising a tubular metal member having a cylindrical body portion and a flange portion provided with a central aperture and secured to one end of said body portion, said body portion, at the portion thereof adjacent to said flange portion, being provided with two diametrically disposed peripheral apertures, a cathode assembly having a cylindrical body portion and an end portion arranged within said tubular member, electron emissive material disposed on said last mentioned end portion, electron accelerating means arranged in spaced cooperative relationship to said emissive end portion, first and second beam intensity control electrodes, each having an active beam forming portion and a planar body portion, said active portions being arranged in spaced abutting relationship between said emissive end portion and said accelerating means and the body portions of said electrodes being arranged substantially in parallel planes and extending through said peripheral apertures, a first electrically insulating member having a central aperture and being secured between and in contact with said flange portion and one side of the body portions of said electrodes, a second electrically insulating member having a central aperture, means to secure said second insulating member in contact with the other side of the body portions of said electrodes, and means fixedly securing said cathode assembly within said tubular member with said electron emissive end portion in spaced adjacency to the active portions of said electrodes.

10. An electron discharge device as claimed in claim 9 wherein said means fixedly securing said cathode assembly Within said tubular member comprises an insulating disc member surrounding said cathode assembly, an annular sleeve coaxial with said cathode body and interposed between said second electrically insulating member and said insulating disc member, and means securing the periphery of said disc member in fixed relationship with the inner surface of said tubular member.

ll. An electrical discharge device adapted to produce two electron beams individually controllable in intensity, comprising a tubular metal member having a cylindrical body portion having a longitudinal central axis and extending into an integral flange portion having a central aperture and partially closing one end of said body portion, said body portion at the portion thereof adjacent to said flange portion being provided with two diametrically disposed peripheral apertures, first and second beam intensity control electrodes, each consisting of a planar member having an active beam forming portion and a body portion, said control electrodes being arranged in a common plane substantially perpendicular to said central axis with the body portions thereof extending through said apertures, the said active portions a cylindrical body portion having a central axis substantially coincident to the central axis of said tubular metal member and an end portion substantially parallel to the plane of said electrodes, electron emissive material disposed on the last mentioned end portion in confronting relationship to the apertures of said active portions, a disc member arranged substantially parallel to the plane of said electrodes surrounding the cylindrical body portion of said cathode body and being arranged with its periphery abutting the inner surface of said tubular metal member, a sleeve member surrounding said cathode body and having one end thereof abutting said second insulating member and the other end thereof abutting one side of said disc member, a metal ring member secured to the inner surface of said tubular metal member and abutting the other side of said disc member and electron accelerating means arranged in spaced cooperative relationship to said active portions of said electrodes and said cathode body.

12. An electrical discharge device as claimed in claim 11 wherein said electrically insulating members consist of mica and said disc and sleeve members consist of an electrically insulating ceramic material.

13. An electron discharge device adapted to produce two electron beams individually controllable in intensity, comprising a tubular member having a body portion and a support member provided with a central aperture secured to one end of said body portion, said body portion being apertured at first and second peripheral regions thereof, a cathode body having an electron emissive surface arranged within said tubular member, electron accelerating means arranged in spaced cooperative relationship to said emissive surface, first and second beam intensity control electrodes each having an active beam forming portion and a body portion, said active portions being arranged in spaced abutting relationship between said emissive surface and said accelerating means and the body portions of said electrodes being arranged substantially in a common plane and extending through said apertured regions, a first electrically insulating member interposed between said support member and one side of the body portion of said control electrodes, a second electrically insulating member, means to secure said second insulating member in abutting relationship to the other side of the body portion of said control electrodes, the body portions of said control electrodes being planar and being held by compression between said insulating members, and means to position said cathode body with the electron emissive surface thereof adjacent to the inner surface of the active portions of said control electrodes.

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